Understanding Acid-Base Reactions: pH Levels of Common Substances

[josephcollins]

Here's another I want to just check with you

The pH of 0.01M Methylammonium chloride (not from the last thread)is lower than 7, correct? As Methylammonium is a weak base and HCl a strong acid?

The pH of potassium cyanide will 7? Both KOH and HCN are very strong?

And finally, the pH of sodium methanoate. This is greater than 7 as Sodium Hydroxide is a strong base and Methanoic acid a weak acid with the OH- predominating?

Thanks,
Joe

 

[wolfson_1123]

Do you know the pH scale?

The pH of potassium cyanide will 7,

No 7 is netrul, 7+ = basic, 7- = acidic.

The pH of potassium cyanide will be = 11 (0.1 N aqueous solution). Use 11.

pH of sodium methanoate = 8-9.5

Methylammonium chloride = 8 (0.1N)

 

[chem_tr]

The pH of 0.01M Methylammonium chloride (not from the last thread)is lower than 7, correct? As Methylammonium is a weak base and HCl a strong acid?

I think it is very close to 7 or 6; according to the neutral point of the water sample used (carbondioxide free water gives a plain 7 pH value, I think).

The pH of potassium cyanide will 7? Both KOH and HCN are very strong?

No. HCN is a very very weak acid, so the pH is even greater than KOH; cyanide is a very strong base since there is a very reactive three-bonded carbon with a non-bonded electron pair.

And finally, the pH of sodium methanoate. This is greater than 7 as Sodium Hydroxide is a strong base and Methanoic acid a weak acid with the OH- predominating?

Yes, this is okay.